1930 Cadillac Brochure Front Cover - GM Heritage Center

12 CADILLAC OPERATOR'S MANUAL
OPERATION 13
position to which it is moved, whereas the accelerator must be held down
to keep the throttle open.
The normal position of the hand lever for driving the car is all the way
up (at "Close"). In this position the throttle of the carburetor is open
just enough to permit the engine to run at idling speed after it is warm.
For starting, however, the lever should be moved approximately one-fourth
the way down, and should be left in this position until the engine is warm
enough to permit the lever to be returned to the idling position without
stalling the engine. (Also see Chapter on "Cold Weather Operation.")
Ignition Control
Correct timing of the ignition in relation to the positions of the pistons
is controlled automatically by the timer-distributor which provides for all
ordinary advancing and retarding of the spark.
A hand control is also provided, however, for further advancing or retarding
of the spark as occasion requires. The hand control is the lever on
the instrument board in front of the steering column. The lever has three
positions, "Starting," "Driving" and "Retard." When starting the engine
in cold weather, the lever should be moved to the "Starting" position, which
is full advance. With the lever in this position the engine will start
more easily and will operate better while warming up.
When starting the engine in mild or warm weather, it is not necessary to
turn the lever to the "Starting" position. The lever can then be left at the
correct "Driving" position for the fuel being used.
After the engine has become warm, the lever should be moved to a position
in the "Driving" range. The correct position of the lever in the "Driving"
range will then depend on the fuel used. Cadillac cars are equipped with
what are known as high compression cylinder heads. These heads enable
the engine to develop more power when used with anti-knock fuel.
The high-compression cylinder heads do not prevent the use of regular
fuel, but when regular fuel is used the spark lever must be retarded more than
is necessary with anti-knock fuel. The spark should be retarded just to
the point where the engine "pings" slightly on rapid acceleration. This
slight amount of spark knock is absolutely harmless to the engine and is
an indication to the driver that the spark is set at the point that will give
maximum power and economy.
Carbon deposit, which accumulates with use in all engines, also causes
spark knock and in time may require setting back the spark. Regardless of
the kind of fuel used or the presence of carbon, the correct setting of the
spark control at any time is at the point where the engine "pings" slightly
on rapid acceleration.
CAUTION—If the engine is being cranked by hand the spark should
always be fully retarded—not moved to "Starting."
Carburetor Enriching Control
The button at the left of the instrument panel (Fig. 5) controls a device
on the carburetor for temporarily enriching the fuel mixture supplied to
the engine. When starting the engine, it is
necessary to have the proportion of liquid
gasoline in the fuel mixture greater than
at other times, because in a cold mixture only
a part of the gasoline is vaporized. Pulling
out the enriching button increases the proportion
of liquid gasoline to air, the normal
proportions being restored when the button
is released and permitted to return to its
original position.
Correct use of the enriching control not
Figure 5. The carburetor enrich- only is essential to quick starting of the
ing control does not prime the car- , , , •
a
buretor. To have any effect, it engine, but also has an important effect on
must be held out while the starter th e life of the engine. The enriching button
is cranking the engine. .
must be pulled out far enough in starting to
provide an explosive mixture quickly so that the battery is not unnecessarily
discharged by useless cranking. The button must also be
held out far enough during the warming-up period so that the engine
will run without missing and "popping back."
On the other hand, it should not be pulled out any further or held out
any longer than is necessary to accomplish these results, because some of
the excess liquid gasoline in the enriched mixture does not burn and washes
off the oil on the cylinder walls, interfering with proper lubrication of the
pistons.
If the engine still retains heat from previous running, the enriching control
should not be used without firstattempting to start the engine on the
normal mixture. If the enriching button is pulled out for starting a hot
engine, the mixture may be made so rich that starting will be impossible.
The enriching button is not a priming device. It has no effect whatever
on the fuel or the fuel mixture unless the engine is being cranked or is run-